The present invention relates to metal beam structures, particularly steel beams, and also to building constructions including such metal beams.
A particular type of metal beam widely used in the construction of buildings, bridges, and other structures, includes a top flange, a bottom flange, and an intermediate web joining together the two flanges. When such a beam is loaded, the top flange is placed under compression, and the bottom flange is placed under tension. Many techniques have been devised for increasing the load-carrying capacity of the beam, e.g., by prestressing the bottom flange in compression to reduce the bending of the beam under load. Examples of various techniques for increasing the load-carrying capacity of the beams are described in U.S. Pat. Nos. 4,144,686, 5,313,749 and 5,704,181.